The average furnace lasts 15 to 20 years. This life span is typical of a furnace with a stainless or aluminized steel heat exchanger. In contrast, old furnaces with heavy metal heat exchangers last for 30 to 40 years, but they are less efficient than newer models, prompting many homeowners to replace them even if they still work.
Once a furnace reaches 15 to 20 years old, its owner should start shopping for a new one. Shopping early allows a homeowner to research the market and leisurely find the best model for their needs. In contrast, if the homeowner waits until the furnace dies, they are forced to shop quickly.
Rising energy bills are usually a sign that the furnace is nearing the end of its lifespan. As furnaces get older, they run less efficiently. Proper maintenance is one way to keep them running efficiently for longer.
As furnaces age, they tend to need a lot of improvements. Homeowners may find themselves spending hundreds of dollars one year just to repeat the pattern the following year. If a furnace is breaking down yearly, it usually indicates that it needs to be replaced. As the furnace ages, it also takes longer to get replacement parts because the repairman usually has to order them.